1. Field of the Invention
The present invention relates to a method for configurating a basic signal allocation unit and a method of transmitting signals using the configurated basic signal allocation unit.
2. Discussion of the Related Art
Generally, there exists a basic unit of resource allocation for signal transmission per communication system. In case of IEEE 802.16e system, a slot is defined as a signal transmission unit. In this case, the slot is a basic data transport unit and can be named ‘minimum resource block’.
The slot in IEEE 802.16e system is described as follows.
First of all, a slot in OFDMA physical layer of IEEE 802.16e system is regulated on both a time domain (e.g., the number of OFDMA symbols) and a frequency domain (e.g., the number of subcarriers) and configurates a data allocation unit. In this case, a definition of OFDMA slot follows OFDMA symbol structure. And, the OFDMA symbol structure may differ in uplink (hereinafter abbreviated as “UL”) or downlink (hereinafter abbreviated as “DL”), in FUSC (full usage of subchannels) or PUSC (partial usage of subchannels), or in distributed subcarrier permutation or adjacent subcarrier permutation.
For instance, for DL FUSC and DL selective FUSC using distributed subcarrier permutation, 1 slot can be defined as 1 subchannel*1 OFDMA symbol.
For DL PUSC using distributed subcarrier permutation, 1 slot can be defined as 1 subchannel*2 OFDMA symbols.
For UL PUSC, DL TUSC (tile usage of subchannels) 1 and TUSC 2 using distributed subcarrier permutation, 1 slot can be defined as 1 subchannel*2, 3 or 6 OFDMA symbols.
FIG. 1 is a diagram for 2-dimensional resource allocation concept in OFDMA of IEEE 802.16e system.
Referring to FIG. 1, in OFDMA of IEEE 802.16e system, a data area becomes a 2-dimensional area consisting of a group 101 of adjacent subchannels and a group 102 of adjacent OFDMA symbols. All resource allocations refer to logical subchannels, and a subchannel offset shown in FIG. 1 becomes a frequency domain reference of resource allocation.
Thus, the 2-dimensional resource allocation of IEEE 802.16e system can be visualized as FIG. 1.
Meanwhile, a distribution method of resource areas supporting each permutation method is explained as follows.
FIG. 2 is a conceptional diagram for a case that resource areas supporting each permutation method are separated on a time axis (left in FIG. 2) and a case that resource areas supporting each permutation method coexist in a specific time (right in FIG. 2).
In the above-mentioned IEEE 802.16e system, a different data allocation structure and a different pilot structure are designed per permutation method (distribution/AMC) and used. This is because the permutation method in the IEEE 802.16e system, as shown in the left side of FIG. 2, is separated on a time axis and because a structure is designed to be optimized for each different permutation method. If various permutation methods, as shown in the right side of FIG. 2, coexist on a certain time instance, i.e., if a user is able to use various permutation methods in a specific time, a single unified basic data allocation structure and a pilot transmission structure would be required.
Meanwhile, in case of a slot used as a basic unit for resource allocation in the IEEE 802.16e system, it can be construed to be relatively small unit in time and frequency domains for supporting small packet service, such as VoIP service. Therefore, it may be disadvantageous because the pilot structure is restricted and overhead increases for signaling even when relatively big packet service is provided.